URANIUM-SERIES DATING OF FOSSIL BONES FROM ALPINE CAVES

During the course of an investigation of fossil cave bear populations the uranium-series method for absolute age determination has been applied to bone material. The applicability of the method to bone samples from alpine caves could be demonstrated by the concordance of U/Th and U/Pa ages and cross-checks with the radiocarbon method. Stratigraphic agreement between bone ages and carbonate speleothetn ages also indicates the potential of the uranium-series method as a suitable tool for the age determination of fossil bones from alpine cave environments.     

Carnivore competition, bone destruction, and bone density

In carnivore-modified archaeofaunal assemblages it is important to evaluate the degree to which carnivores have overprinted hominin behavioral signals. To examine the signals of increased competition for discarded bone, we present controlled experimental data on 33 simulated archaeological sites subjected to secondary consumption by spotted hyenas. We examine the relationship between competition, as measured by controlled numbers of hyenas and limb bones, and resultant levels of destruction and correlations between long-bone portion survivorship and bone density. Our results indicate that levels of destruction are equivalent regardless of the numbers of hyenas or long-bones included in the experimental assemblages. Correlations between long-bone epiphyseal and near-epiphyseal portions and bone density, however, do provide an indication of the level of competition. Results from the experimental study are used to highlight divergent levels of carnivore competition for hominin-discarded bone at the Plio-Pleistocene localities FLKN-Zinjanthropus and FLKN levels 1–2 from Olduvai Gorge, Tanzania.     

An experimental study of large mammal bone modification by crocodiles and its bearing on the interpretation of crocodile predation at FLK Zinj and FLK NN3

The taphonomic signature of crocodiles as agents of bone modification has been previously identified by specific tooth mark types (e.g., bisected pits) and by a conspicuous presence of these marks: more than 75% of bones modified by crocodiles bear at least one of these distinctive marks. Therefore, crocodile tooth-marking would be notably prevalent in bone assemblages resulting from crocodile predation and active scavenging. The present study contributes to refine this diagnosis by showing greater variability of these types of marks, a different degree of tooth-marking intensity, and a somewhat different distribution of tooth-marked elements according to skeletal parts from previous experiments with crocodiles. Some of these differences are due to different experimental variables and conditions and this highlights the need to understand behavioral variability in crocodile ecological settings. This variability in crocodile tooth-marking probably results from several as-yet-inadequately measured behavioral and ecological factors, such as intensity of feeding competition and differences between male and female crocodile feeding behaviors, among others. Furthermore, this study also contributes to a better definition of the microscopic criteria that can be used to distinguish crocodile-inflicted marks from other types of bone surface modifications. In light of these and previous experimental frameworks, we reevaluate the application of these analogs to modifications documented in hominin fossils from Olduvai Gorge (OH8 and OH35) and the resulting inferences about the hazard posed by crocodiles on the paleolandscape where FLK North North and FLK Zinj (Bed I) were formed. The taphonomic analysis also shows that Olduvai OH8 and OH35 were probably not preyed upon by crocodiles. It is concluded that no tangible evidence can be used to support the interpretation that OH35 was modified by crocodiles and that the overall presence of crocodiles in FLK North North and FLK Zinj was rather marginal, based on the virtual absence of crocodile-modified bones in both archaeofaunal assemblages.     

RESEARCH NOTES AND APPLICATION REPORTS ELEMENT DISTRIBUTION MAPS IN FOSSIL BONES

The combined application of fission track analysis and neutron activation-induced β-autoradiography to map the trace element distributions of scandium, cobalt, uranium and rare earth elements in fossil bone samples from East Africa is described. Both uranium and the rare earth elements are incorporated into bone apatite during fossilisation, whereas scandium and cobalt occur additionally in any iron-manganese minerals precipitated in pore spaces within the bone cortex. The distribution of uranium is different from that of the rare earth elements in the fossil bone cortices; it enters fossil bone more rapidly and is sensitive to changes in the redox potential of the palaeogroundwater.     

Application of GIS methods to retrieve orientation patterns from imagery; a case study from Beds I and II,Olduvai Gorge (Tanzania)

The role of natural processes in the formation of the Bed I and II sites at Olduvai Gorge (Tanzania) remains the subject of much debate, five decades after their original excavation. Preferred orientation of items is indicative of water disturbance, but compass bearings were not available in Mary Leakey's (1971) study. Using GIS methods, we have vectorized maps from 1960s excavations at Olduvai, and applied a range of statistical techniques to calculate items strike. The GIS analysis suggests strongly preferred orientation patterns in Bed I, and more heterogeneous angular histograms in Bed II. Two complementary lines of evidence support these results. Firstly, modelling of potential mapping errors provides a large interval of confidence for preferred orientation patterns. Second, the GIS study was extended to photographs of the earlier excavations and to maps from recent fieldwork at Olduvai; both yielded patterned arrangement of lithics and bones, and are consistent with results based on the analysis of the 1960s maps, i.e. a large number of the Bed I and II assemblages are preferentially oriented. These results highlight the potential of GIS applications to the analysis of imagery in Stone Age studies, and bear important implications for the understanding of the role of natural agents in site formation processes at Olduvai.     

The Transition to the Acheulean in East Africa: an Assessment of Paradigms and Evidence from Olduvai Gorge (Tanzania)

The origin of the Acheulean constitutes a key aspect of current research in the archaeology of human evolution. Olduvai Gorge is one of the main sites in Africa in the study of the transition from the Oldowan to the Acheulean, due to both the uniqueness of its archaeological record, and the influence of early investigations at Olduvai on the development of Early Stone Age research. This paper reviews the impact of work at Olduvai in shaping a modern view of cultural evolution from the Oldowan to the Acheulean. It also evaluates the lithic assemblages excavated by Mary Leakey in Olduvai Middle and Upper Bed II, based on a first-hand review of the collections. We conclude that previous paradigms used to explain inter-assemblage variability are not superseded as much as generally assumed, and that a modern view of the origins of the Acheulean requires a reassessment of the cultural, biological, and paleoecological evidence at Olduvai and elsewhere in Africa.     

URANIUM VARIATIONS IN A DATED FOSSIL BONE SERIES FROM OLDUVAI GORGE,TANZANIA

Of twelve elements analyzed in a series of bovid teeth from the Olduvai Gorge, uranium is the only element which varies appreciably with the ages of the samples. Uranium concentrations increase at first, then decrease with increasing age, and therefore cannot be used by themselves to obtain absolute or even relative ages of the samples. A model accounting for the behaviour of uranium is proposed in which uranium is absorbed in the samples during the decay of organic material and is lost after this decay ceases. If one accounts for uranium losses, the concentrations of uranium and its decay products may be used to accurately date skeletal material from the Olduvai gorge.     

Avian taphonomy: observations at two Magellanic penguin (Spheniscus magellanicus) breeding colonies and their implications for the fossil record

Actualistic studies on vertebrate taphonomy have centred on mammals, and to a much lesser extent on flying birds. Members of the Spheniscidae are anatomically specialized making it problematic to make direct inferences from previous taphonomic work. Modern bone assemblages from two Spheniscus magellanicus breeding colonies on the southern Atlantic coast of continental Patagonia, Argentina, were surveyed on foot along linear transects, and features were determined that are useful in interpreting the fossil record. Present day bone accumulations have specific properties resulting from penguin anatomy and osteology as well as from the composition of the vertebrate community and regional environmental conditions. Most salient are the high spatial density of bones, the dominance of Spheniscidae remains over those of other vertebrates, the high percentage of disarticulated bones, the predominance of limb bones, the low frequencies of carnivore bone modifications, and the abundance of fractured bones. Many of these features observed in the modern assemblages can be identified in fossil avian bone deposits.     

U-series dating of soda straw stalactites from excavated deposits: method development and application to Blanche Cave, Naracoorte, South Australia

This study aimed to further test the method, reported by St Pierre et al. (2009), to develop robust chronologies of deposits in limestone caves through U/Th (Uranium/Thorium or U-Series) dating of soda straw stalactites. The chronology of fossil bearing deposits at Blanche Cave was further constrained with thermal ionisation mass spectrometry (TIMS) U/Th dating of 17 additional soda straw stalactite samples, and results were compared to recalibrated ¹⁴C ages of charcoal. The results support the assertion that soda straw stalactites can provide ages close to the time of sediment deposition and may be used as reliable chronological markers, particularly for periods reaching or beyond the radiocarbon dating limit. The application of an enhanced cleaning technique facilitated the reduction of detrital Th in samples, significantly increasing age accuracy and precision. Additionally U/Th age accuracy and precision was increased through the application of site-specific measured U/Th ratios to correct for the detrital ²³⁰Th component in samples.     

Bone Degradation and Environment: Understanding,Assessing and Conducting Archaeological Experiments Using Modern Animal Bones

Archaeological experiments that use modern bones to replicate past animal bone assemblages have often failed to consider the effects of environment, storage and preparation on modern bones. Often, these experiments make little mention of the conditions to which bones were subject during their storage and preparation for use in experiments. In other instances, these variables are reported but not considered as factors that contribute to the nature of the results obtained. This study considers previously reported data concerning the degradation of frozen bones (−20°C), and bones exposed to hot, dry conditions (40°C), and presents new data for bones exposed to room temperature environments (22°C) and refrigerated environments (2°C), and bones that are frozen (−20°C) and then thawed (22°C). These conditions are all relevant to understanding the nature of bone degradation and the use of bones in modern archaeological experimentation. This article also surveys a range of previously reported experiments that utilise modern bones to create analogies to the past and considers different methodological approaches and their relationship to the condition of bones at the time of their fracture and fragmentation. The longitudinal data presented in this study demonstrate differential rates of bone degradation over time in various environmental conditions. This degradation results in dramatic changes in bone fracture morphology, bone strength and utility for bone tool production. These observations have significant implications for experiments that utilise modern bones, especially when experimental data are used to create analogies to the archaeological past. Copyright © 2012 John Wiley & Sons, Ltd.     

The long–term survival of bone: the role of bioerosion

Fossil bones (N = 350) spanning more than 350 million years, and covering a wide range of depositional environments, were studied to compare the distribution of microbial destruction features in fossil bones with previously published data sets of bones of archaeological age. The distribution of bioerosion in fossil bones is very different from that found in bone from archaeological sites. Fossil bones typically show little or no bioerosion. Under normal conditions, if a bone is to survive into the fossil record, then rapid bioerosion must be prevented (or halted). This conclusion suggests that early post mortem processes,such as the mode of death, influence the potential of any bone to survive into deep time.     

Effects of distance from stone source on landscape-scale variation in Oldowan artifact assemblages in the Paleo-Olduvai Basin,Tanzania

Ongoing excavations at Olduvai Gorge, Tanzania, reveal tremendous variability among stone artifact assemblages across the Plio-Pleistocene Olduvai Lake Basin during Bed I and lower Bed II times. Theoretically, stone artifact traces of Oldowan hominin land use are determined by the distribution of larger mammal carcasses and arboreal refuge from predation as well as proximity to stone material sources.     

Microscopic examination of ground sections – a simple method for distinguishing between bone and antler?

Both bones and antlers have been used throughout history for manufacturing various products. Therefore, archaeologists often have to distinguish between these materials. The more the raw material (bone or antler) has been treated, the more complicated it is to distinguish. For this study, recent macerated and archaeological samples of bone and antler and their products have been compared. Antler is usually very easy to distinguish based on the characteristic surface structure; however, the original surface is not preserved in all artefacts. The inner surface of the diaphysis of long bones is mostly compact with prominent trabeculae and lamellae, whereas, after removal of the spongiosa, the inner surface of antler is characterised by numerous grooves. Sometimes, however, artefacts are found which are composed only of the compact bone substance, without inner and outer surfaces, and it is not possible to distinguish between bones and antlers macroscopically. Haversian systems can be found in histological and ground sections of both bones and antlers. In contrast to bones, antlers have few interstitial lamellae. The osteons of antler seem to be smaller and to consist of fewer layers than those of bone. Inner and outer circumferential lamellae cannot be distinguished in antlers. Although microscopic examination of sectioned samples does not allow distinction between bones and antlers in every case, it represents a valuable additional tool for distinguishing between these two materials in historic artefacts. Copyright © 2007 John Wiley & Sons, Ltd.     

Taphonomic modifications produced by modern brown bears (Ursus arctos)

Actualism has been a fundamental tool in taphonomy. The knowledge of accumulation patterning of modern faunal allows us to interpret the activity of different actors in the archaeological record and to reconstruct the behaviour of preterit animals and humans in which we are interested. However, until now, there are few works that include bone modifications made by bears amongst those made by carnivores. Most data about bone modifications made by bears have been obtained from the archaeo‐palaeontological record. In most of these assemblages, the presence of bears is related to their period of hibernation. Therefore, in these contexts, the changes documented on recovered bear bones are associated only with cannibalism. In this paper, we present an actualistic study about modifications on bones made by modern brown bears. These animals can cause damage similar to those produced by other large carnivores. Generally, bear activity leaves slight damage, mainly on large‐sized animal bones. However, on bones of small‐sized animals and those of greater fragility, the bears can produce abundant damage. Though not usual, bears can break long bones and consume the complete epiphysis. This study suggests that bears have the potential to be agents of bone modification in fossil assemblages. Consequently, they should be considered as a possible agent of modification of faunal remains in the fossil record. Copyright © 2011 John Wiley & Sons, Ltd.     

Hominid–Carnivore Coevolution and Invasion of the Predatory Guild

Coevolution is defined as reciprocal selective pressures that operate to make the evolution of one taxon partially dependent on the evolution another. This process often involves multiple species exploiting shared limiting resources. In classic coevolutionary models, populations of sympatric species are seen to diverge in one or more morphological, ecological, or behavioral traits to effect more even partitioning of resources and reduce levels of interspecific competition. Character displacement and resource partitioning are thought to be central not only to how species coexist on limited resources, but also to how species invade new resource niches. Hominid invasion of the predatory guild at least 2 my ago would have brought them into contact with a range of new selective pressures including competition with a number of large-bodied predators. This study explores resource partitioning between hominids and other Plio-Pleistocene large-bodied predators through analyses of predator food transport strategies. The anatomical content (head/limb MNE) of hominid transported faunal assemblages at Bed I Olduvai and FxJj 50 (Koobi Fora), when compared to modern predator control cases, suggests that Plio-Pleistocene hominids practiced food transport strategies intermediate between those of top predators such as wolves and those of confrontational scavengers such as spotted hyaenas. Plio-Pleistocene hominid food transport strategies do not resemble those of nonconfrontational scavengers such as brown and striped hyenas. The highly regular patterns differentiating bone assemblages accumulated by top predators, hominids, and confrontational and nonconfrontational scavengers suggest that hominid invasion of the predatory guild involved resource partitioning potentially based on some form of character displacement.     

Early hominid behaviour and culture tradition: raw material studies in Bed II,Olduvai Gorge

Two studies involving an analysis of artefact raw material use in Bed II at Olduvai Gorge (1.6–1.4 myr) are reported. The first study shows evidence for the manufacture of chert artefacts at a factory site and the subsequent transport of selected whole flakes to another site for use. Early hominids are thus shown to have been capable of planning a sequence of activities involving raw material extraction, processing, selection and transport for an ultimate use. The transported artefacts are found accumulated at sites associated with animal bones, suggesting that hominids were a principal agent in site formation. The second study demonstrates that the attributes of the artefacts said to differentiate the Developed Oldowan B from the Early Acheulean at Olduvai Gorge are the result of differential raw material use.

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Résumé Deux études sur l'analyse de la matière première utilisée pour les outils du Bed II d'Olduvai Gorge (1.6–1.4 myr) sont présentées. La première étude prouve que les outils en chert étaient fabriqués dans un atelier de taille et que des éclats entiers étaient sélectionnés et transportés afin d'être utilisés sur un autre site. Ceci démontre que les anciens hominidés étaient capables de planifier une séquence d'activités comprenant l'extraction, le traitement, la sélection et le transport pour utilisation ultérieure, de la matière première. Les outils transportés sont retrouvés accumulés sur les sites, associés à des ossements d'animaux, ce qui suggère que les hominidés étaient les principaux responsables de la formation des sites. La deuxième étude démontre que les attributs des outils/objets sensés différencier l'Oldwayen développé B de l'Acheuléen ancien à Olduvai Gorge résultent d'une utilisation différente de la matière première.

     

Mobility, competition, and Plio-Pleistocene hominid foraging groups

Evidence for carcass access times and levels of early hominid mobility is synthesized using studies of carnivore ethology and theories of interspecific competition to arrive at tentative conclusions about the organization of Plio-Pleistocene hominid foraging groups. The model presented suggests that group foraging tactics, in combination with high mobility, are central to successful confrontational scavenging (interference competition), whereas individual foraging tactics and high mobility are central to successful nonconfrontational scavenging (exploitative competition). In contrast, group or individual foraging tactics and low mobility characterize the acquisition of fresh carcasses in low-competition contexts. Individual foraging tactics and low mobility are employed in response to extreme competition over marginal resources. Preliminary tests with data from Bed I Olduvai Gorge and Koobi Fora suggest that Plio-Pleistocene hominids, like other large-bodied predators, employed flexible foraging tactics involving changes in group size and levels of mobility to gain access to carcasses in both low-and high-competition contexts.     

Fluvial dispersal potential of guanaco bones (Lama guanicoe) under controlled experimental conditions: the influence of age classes to the hydrodynamic behavior

Hydrodynamic sorting is a taphonomic process able to transport and scatter bones deposited in archaeological and paleontological sites. This study presents the results of experimentation performed in an artificial flume with guanaco (Lama guanicoe) bones of different ontogenetic development, dry and saturated in water, in hydric flows velocities of 15 and 30 cm/s. The obtained results show that bone global density, the age of the individual, the dry or wet bone state, and the hydric flow velocity influence significantly bone dispersion. In this way, bones from immature individuals with unfused secondary growth centers and relatively low bulk density have better possibility of being transported than fused bones from adult individuals. Taking into account the results obtained in this experimentation and the feasibility of discriminating age categories in fossil assemblages, two bone groups with differential potential transport are presented in this paper. These transport groups constitute a methodological tool to evaluate the role hydric current may had played in the formation of a fossil assemblage.     

Flint and Quartzite: Distinguishing Raw Material Through Bone Cut Marks

Since the 1980s, several experimental analyses have been able to differentiate some lithic tool types and some of their raw materials according to the morphology of cut marks imprinted by such tools when used for butchering activities. Thus, metal tool use has been differentiated in contexts with an abundance of lithic tools, or even the use of hand axes has been documented in carcass processing, in contrast with simple unretouched or retouched flakes. As important as this information is, there are still other important aspects to be analysed. Can cut marks produced with different lithic raw material types be differentiated? Can cut marks made with different types of the same raw material type be characterized and differentiated? The objective of this study is to evaluate if cut marks resulting from the use of different flints and different quartzites are distinguishable from each other. In the present work, an experimental analysis of hundreds of cut marks produced by five types of flint and five varieties of quartzite was carried out. Microphotogrammetry and geometric–morphometric techniques were applied to analyse these cut marks. The results show that flint cut marks and quartzite cut marks can be characterized at the assemblage level. Different types of flint produced cut marks that were not significantly different from each other. Cut marks made with Olduvai Gorge quartzite were significantly different from those produced with a set comprising several other types of quartzites. Crystal size, which is larger in Olduvai Gorge quartzites (0.5 mm) than Spanish quartzites (177–250 μm), is discussed as being the main reason for these statistically significant differences. This documented intra‐sample and inter‐sample variance does not hinder the resolution of the approach to differentiate between these two generic raw material types and opens the door for the application of this method in archaeological contexts.     

Bone frequencies: differential transport, in situ destruction,and the MGUI

Human transport of bones with high food values, and destruction of bones with low density values are the traditionally invoked explanations of the frequencies of bones in archeological contexts. The manner in which these two explanations have been used suggests archaeologists assume the explanations to be independent of one another. The transport explanation is operationalized as the modified general utility index (MGUI) of Binford, and the destruction explanation is operationalized with measures of bone density. Statistical correlation of the MGUI with bone density, while weak, indicates that many high utility bones have low density values while many low utility bones have high density values. Because low density bones tend to be destroyed more readily than high density bones, inferences of human utility strategies derived from bone frequencies and based on the MGUI may be inaccurate. The utility strategies suggested by three archaeofaunas are compared to bone density, and two of these faunas are shown to potentially be the result of differential destruction and not human transport as measured by the MGUI.